Re: [PATCH v4 3/4] USB: Add a function to obtain USB version independent maximum bpi value

[Mathias Nyman <mathias.nyman@linux.intel.com>]

Hi

On 18.8.2025 9.08, Sakari Ailus wrote:
> Hi Michał,
> 
> Thank you for the review.
> 
> On Wed, Aug 13, 2025 at 04:49:58PM +0200, Michał Pecio wrote:
>> On Tue, 12 Aug 2025 16:24:44 +0300, Sakari Ailus wrote:
>>> From: "Rai, Amardeep" <amardeep.rai@intel.com>
>>>
>>> Add usb_endpoint_max_isoc_bpi() to obtain maximum bytes per interval for
>>> isochronous endpoints in a USB version independent way.
>>>
>>> Signed-off-by: Rai, Amardeep <amardeep.rai@intel.com>
>>> Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
>>> Co-developed-by: Sakari Ailus <sakari.ailus@linux.intel.com>
>>> Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
>>> Reviewed-by: Hans de Goede <hansg@kernel.org>
>>
>> Hi,
>>
>> This is practically identical to xhci_get_max_esit_payload().
>>
>> Couldn't xhci also use this helper now, to reduce duplication and
>> ensure that it has the same idea of ESIT payload as class drivers?
>>
>> Note that this here would need to also accept interrupt EPs:
>>> +{
>>> +	if (usb_endpoint_type(&ep->desc) != USB_ENDPOINT_XFER_ISOC)
>>> +		return 0;
> 
> Sounds reasonable, I'll see how to best take that into account in v5.
> 
> I wonder if I should adopt the name from the xHCI variant as the function
> would be also used for interrupt endpoints.
> 

I think the "ESIT" acronym (Endpoint Service Interval Time) is very xHCI spec
specific. Usb spec usually refers to isoc and interrupt endpoints as "periodic"

how about one of these:
usb_endpoint_max_periodic_bytes()
usb_endpoint_max_periodic_payload()
usb_endpoint_max_periodic_bpi()

Thanks
Mathias